Certain refrigerator appliances include sealed systems for cooling chilled chambers of the refrigerator appliances. The sealed systems generally include a compressor that generates compressed refrigerant during operation of the sealed systems. The compressed refrigerant flows to an evaporator where heat exchange between the chilled chambers and the refrigerant cools the chilled chambers and food items located therein.
Recently, certain refrigerator appliances have included linear compressors for compressing refrigerant. Linear compressors generally include a piston and a driving coil. The driving coil receives a current that generates a force for oscillating the piston (i.e., sliding the piston forward and backward within a chamber having a cylinder head). An elastic element, such as a spring, may be provided to aid in such oscillation. During motion of the piston within the chamber, the piston compresses refrigerant. Generally, the force of gas compression acts to push the piston away from the chamber and cylinder head.
Motion of the piston within the chamber may be controlled such that the piston does not crash against another component of the linear compressor during motion of the piston within the chamber. Such head crashing can damage various components of the linear compressor, such as the piston or an associated cylinder. Nonetheless, the net positive force of gas compression may act to shift or offset the center of equilibrium for oscillation. Such an offset may cause the elastic element to extend more in one oscillation direction (e.g., a positive direction away from the chamber) than in the opposite oscillation direction (e.g., a negative direction toward the chamber). In some instances, the imbalanced extension of the elastic element and the piston may increase the fatigue (e.g., fatigue loading) of certain elements within the linear compressor. Moreover, the rate of part failure may increase and operational life may decrease.
Although unbalanced extension and increased fatigue (e.g., through extreme or excessive spring extension) is preferably avoided, it can be difficult to determine a position of the piston and magnitude of displacement within the chamber. For example, a stroke length of the piston is dependent upon a variety of parameters of the linear compressor, and such parameters can vary. Determining a stroke length or position of the piston can be especially difficult if the linear compressor is inadvertently wired in an opposite direction from the direction intended by the manufacturer (e.g., such that polarity of the voltage and current within the linear compressor is reversed). In addition, utilizing a sensor to measure the stroke length of the piston can require sensor wires to pierce a hermetically sealed shell of the linear compressor. Passing the sensor wires through the shell provides a path for contaminants to enter the shell. Moreover, utilizing a sensor may present other challenges, such as sensitivity to electrical noise, increased costs, and the potential for sensor failure that may contribute to in failure of the linear compressor.
Accordingly, it would be useful to provide a linear compressor and method of operation for addressing one or more of the above-identified issues. In particular, a linear compressor and method for determining or addressing the polarity of a supplied voltage and current would be especially advantageous.